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Glass bubble insulation coatings research

2015-01-06 04:04:53 77
Hollow glass bubble fifties and sixties of the 20th century developed a particulate material, thin-walled borosilicate material from sodium made by a special process, closed the tiny sphere, the sphere inside the parcel certain amount of gas, it has low-density, high-low thermal conductivity, low oil absorption, high temperature resistance, dielectric strength, good thermal stability, corrosion resistance, controllable particle size and chemical composition and so on. With the development of science and technology as well as industrial mass production of hollow glass bubble achieve low hollow glass bubble material prices, variety, size increasing, can be widely used in building materials, plastics, rubber, paint, metallurgy, marine and aerospace and other fields. The main expand about this point in insulation performance.
In general, the thermal conductivity of the insulating material is conduction combined effect of convection and radiation. Skochdopote noted that the hole diameter of less than 4mm gas bubble does not occur natural convection, glass bubble diameter is typically between a few micrometers to several hundred micrometers, it may not be considered natural convection of air. In non-high-temperature radiation heat transfer of a small proportion of the total, it can not consider the thermal radiation. Effect of reduced strength insulating material is heat-exchanged, and functions to impede heat transfer characteristics. Film material / glass bubble composite coatings are three-phase composite material comprising an organic film-forming materials and other ingredients to form a continuous phase organic additives, hollow glass bubble spherical shell phase and gas phase. In the heat transfer process, when faced hollow glassbubble, only a small portion of the heat conduction through the glass bubble, while most of the heat is bypassed glass bubble, due to the glass bubble of low thermal conductivity, and the heat transfer path in the coating becomes long and complicated, resulting in heat transfer performance, according to the law and the minimum thermal resistance than the equivalent thermal conductivity equal rules, as long as the composite coating unit body and overall have equal than the equivalent resistance, regardless of the size scale unit body, when considering only the thermal conductivity, which means the whole body and the equivalent thermal conductivity equal.
Calculation of equivalent thermal conductivity of the composite coating, and comes down to the same ratio to calculate the equivalent resistance of the cell body of the equivalent thermal conductivity can be seen.